Abstract

Elevated levels of background risk have been shown to elicit changes in behaviour, physiology, morphology, and cognitive function. While there is a growing body of research investigating how various aspects of the environment influence brain growth, research examining neuroplastic responses to local predation is lacking. Using lab-reared convict cichlids (Amitatlania nigrofasciata) as a model species, I tested the hypothesis that neuroplastic responses will vary between two levels of perceived predation risk in both juveniles and adults. In a series of laboratory trials, convict cichlids at two different ontogenetic stages (juveniles and adults) were exposed to either the alarm cues of injured conspecifics (high risk) or distilled water (low risk). When juvenile convict cichlids were exposed to high risk cues, they showed a significant increase in olfactory bulb size (19.7%) compared to the low-risk control. Additionally, all brain regions, when exposed to high risk cues, increased in size when compared to the low risk group: 13.5% in the telencephalon, 20.8% in the optic bulb, 11.9% in the cerebellum, and 18.2% in the hypothalamus. Overall the entire brain increased by 16.2% when compared to the low risk group, however no allometric growth of any single brain region was observed. Unlike the results seen in juveniles 1 day post treatment, examination of adult cichlid brains revealed no difference in olfactory bulb size, or any brain region, between the high and low risk groups. Furthermore, high risk juveniles that were given an 11-day latency period following treatment, showed no significant difference in any brain region, including olfactory bulb size, when compared to those given distilled water. Taken together these results suggest that juvenile cichlids may exhibit a bidirectional neuroplastic response to high risk cues and that these responses are ontogenetically constrained.